1. Field of the Invention
The present invention relates to a particle adhesion preventing member, for example, which prevents adhesion of particles such as toner and the like that scatter in an image forming apparatus, and an image forming apparatus, such as a copying machine, a printer, a facsimile machine, and a multifunctional peripheral thereof, equipped with such a particle adhesion preventing member.
2. Description of the Related Art
Conventionally, a primary charging device, an exposure device, a developing device, a transfer device, a cleaning device, and the like are arranged at specified positions along a circumference of a photosensitive drum in an image forming apparatus to which an electrophotographic system is applied. A toner image formed on the photosensitive drum is transferred onto a recording material directly or through an intermediate transfer belt. In such an image forming apparatus, power toner is housed in a developing container in the developing device, and supplied to the photosensitive drum by rotating a developing sleeve.
At that time, the toner is scattered around due to an electric field between the developing sleeve and the photosensitive drum as well as a centrifugal force of the developing sleeve. The toner in the developing container is sometimes also blown out and scattered around from a space between the developing sleeve and the developing container due to air flow that occurs by stirring the toner in the developing container.
Also in the case of an image forming apparatus equipped with an intermediate transfer belt, mechanical rubbing is given to the toner in a primary transfer portion that is a contact portion of the photosensitive drum and the intermediate transfer belt, so that the toner sometimes scatters. This occurs similarly in a secondary transfer portion in which the toner image is transferred from the intermediate transfer belt onto the recording material. The toner image on the intermediate transfer belt sometimes also scatters by the centrifugal force with movement of the intermediate transfer belt.
The toner that has scattered in this way is typically captured by a filter provided on a ventilation fan. However, when the toner excessively scatters in the device or adheres to a particular site, it causes an image failure or maintenance of the device becomes hard. Thus, technology that prevents such scattering or adhesion of the toner has been proposed conventionally.
For example, the technology has been proposed in which for the toner that scatters from the space between the developing sleeve and the developing container, a surface opposed to the developing sleeve in the developing container is provided with an electrode, to which voltage bias with the same polarity as a charging polarity of the toner is applied (Japanese Patent Application Laid-Open No. 7-209987).
Also the technology has been proposed in which the scattering of the toner that occurs on an upper side of the developing device is prevented by arranging a plurality of electrodes in a circumference direction on a more upstream side of a rotation direction of the photosensitive drum than a position to be developed in the developing device and applying thereto alternating voltage, a phase of which is shifted (Japanese Patent Application Laid-Open No. 5-35112).
Also the technology has been proposed in which the toner is prevented from adhering onto a light-emitting surface of an LED array by providing an electrode around the LED array in the exposure device and applying the alternating voltage thereto (Japanese Patent Application Laid-Open No. 2006-239919).
The technology to aspirate the scattered toner by the use of an aspirating device and a duct has been also proposed (Japanese Patent Application Laid-Open No. 2007-33587).
The technology has been proposed in which toner contamination on the recording material is prevented by providing a recording material guiding member upstream of the secondary transfer portion with a conductive non-contact toner capture member and applying a strong bias thereto thereby capturing the scattering toner (Japanese Patent Application Laid-Open No. 2008-3449).
However, when the device for applying the voltage, the device for aspirating the toner and the duct, and the like are provided in order to prevent the scattering and adhesion of the toner as described in the aforementioned patent references, the apparatus increases in cost and size.
On the other hand in recent years, with downsizing the image forming apparatus, the technology as aforementioned to lead an increased size of the apparatus is difficult to be introduced. Also in the case of such a downsized apparatus, the space between the parts is narrow and the toner contamination occurs easily. Therefore, cleaning by a service engineer must be frequently performed and it takes a long time to clean the apparatus. Thus, a maintenance cost is increased. Particularly in the case of a high speed image forming apparatus, the toner tends to scatter more frequently and the maintenance cost is more easily increased.